You forgot Satoshi's 1000000 bitcoins that have newer been moved, but still have their public keys visible.
Those addresses are difficult to protect from QC, because even if we implement a QC-resistant algorithm, those can't be protected or otherwise even Satoshi couldn't move them.
That's quite interesting, I didn't know that. I couldn't find anything useful on Google, got any more info on that? How are the public keys to Satoshi's old stash known, where public keys public before the protocol was changed to the way it works now?